US20140060031A1 - Hydraulic control system having swing energy recovery - Google Patents
Hydraulic control system having swing energy recovery Download PDFInfo
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- US20140060031A1 US20140060031A1 US13/718,907 US201213718907A US2014060031A1 US 20140060031 A1 US20140060031 A1 US 20140060031A1 US 201213718907 A US201213718907 A US 201213718907A US 2014060031 A1 US2014060031 A1 US 2014060031A1
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- fluid
- accumulator
- pressure
- swing motor
- pump
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B1/00—Installations or systems with accumulators; Supply reservoir or sump assemblies
- F15B1/02—Installations or systems with accumulators
- F15B1/027—Installations or systems with accumulators having accumulator charging devices
- F15B1/033—Installations or systems with accumulators having accumulator charging devices with electrical control means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B1/00—Installations or systems with accumulators; Supply reservoir or sump assemblies
- F15B1/02—Installations or systems with accumulators
- F15B1/024—Installations or systems with accumulators used as a supplementary power source, e.g. to store energy in idle periods to balance pump load
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B13/00—Details of servomotor systems ; Valves for servomotor systems
- F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
- F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
- F15B21/08—Servomotor systems incorporating electrically operated control means
- F15B21/082—Servomotor systems incorporating electrically operated control means with different modes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
- F15B21/14—Energy-recuperation means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
- F15B2211/205—Systems with pumps
- F15B2211/2053—Type of pump
- F15B2211/20546—Type of pump variable capacity
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
- F15B2211/21—Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge
- F15B2211/212—Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge the pressure sources being accumulators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/63—Electronic controllers
- F15B2211/6303—Electronic controllers using input signals
- F15B2211/6306—Electronic controllers using input signals representing a pressure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/63—Electronic controllers
- F15B2211/6303—Electronic controllers using input signals
- F15B2211/6306—Electronic controllers using input signals representing a pressure
- F15B2211/6313—Electronic controllers using input signals representing a pressure the pressure being a load pressure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/63—Electronic controllers
- F15B2211/6303—Electronic controllers using input signals
- F15B2211/6336—Electronic controllers using input signals representing a state of the output member, e.g. position, speed or acceleration
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/665—Methods of control using electronic components
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/665—Methods of control using electronic components
- F15B2211/6652—Control of the pressure source, e.g. control of the swash plate angle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/665—Methods of control using electronic components
- F15B2211/6658—Control using different modes, e.g. four-quadrant-operation, working mode and transportation mode
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
- F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
- F15B2211/7058—Rotary output members
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/80—Other types of control related to particular problems or conditions
- F15B2211/86—Control during or prevention of abnormal conditions
- F15B2211/8603—Control during or prevention of abnormal conditions the abnormal condition being an obstacle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/80—Other types of control related to particular problems or conditions
- F15B2211/875—Control measures for coping with failures
- F15B2211/8752—Emergency operation mode, e.g. fail-safe operation mode
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/80—Other types of control related to particular problems or conditions
- F15B2211/88—Control measures for saving energy
Definitions
- the present disclosure relates generally to a hydraulic control system and, more particularly, to a hydraulic control system having swing energy recovery.
- Swing-type excavation machines for example hydraulic excavators and front shovels, require significant hydraulic pressure and flow to transfer material from a dig location to a dump location.
- These machines direct the high-pressure fluid from an engine-driven pump through a swing motor to accelerate a loaded work tool at the start of each swing, and then restrict the flow of fluid exiting the motor at the end of each swing to slow and stop the work tool.
- U.S. Pat. No. 7,908,852 of Zhang et al. that issued on Mar. 22, 2011 (the '852 patent).
- the '852 patent discloses a hydraulic control system for a machine that includes an accumulator.
- the accumulator stores exit oil from a swing motor that has been pressurized by inertia torque applied on the moving swing motor by an upper structure of the machine.
- the pressurized oil in the accumulator is then selectively reused to accelerate the swing motor during a subsequent swing by supplying the accumulated oil back to the swing motor.
- the hydraulic control system of the '852 patent may help to improve efficiencies of a swing-type machine in some situations, it may still be less than optimal.
- some pressurized fluid exiting the swing motor may still have useful energy that is wasted.
- there may be situations during operation of the hydraulic control system of the '852 patent for example during deceleration and accumulator charging, when a pump output is unable to supply fluid at a rate sufficient to prevent cavitation in the swing motor.
- the machine may operate differently under different conditions and in different situations, and the hydraulic control system of the '852 patent may not be configured to adapt control to these different conditions and situations.
- the '852 patent does not disclose operational control during a stall condition.
- the disclosed hydraulic control system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.
- the hydraulic control system may include a tank, a pump configured to draw fluid from the tank and pressurize the fluid, and a fluid actuator driven by a flow of pressurized fluid from the pump.
- the hydraulic control system may further include an accumulator configured to selectively receive pressurized fluid discharged from the fluid actuator and selectively supply pressurized fluid to the fluid actuator.
- the hydraulic control system may also include a pressure sensor configured to generate a signal indicative of a pressure of the accumulator, a charge valve configured to regulate fluid flow into the accumulator, a discharge valve configured to regulate fluid flow out of the accumulator, and a controller in communication with the control valve, the charge valve, and the discharge valve.
- the controller may be configured to detect stall of the fluid actuator, to make a comparison of the pressure of the accumulator with a threshold pressure, and to selectively move the charge valve to charge the accumulator or move the discharge valve to discharge the accumulator during the stall based on the comparison.
- the present disclosure is directed to method of operating a hydraulic control system.
- the method may include drawing fluid from a tank and pressurizing the fluid with a pump.
- the method may also include selectively directing pressurized fluid to a fluid actuator and from the fluid actuator to the tank to move the fluid actuator.
- the method may further include collecting pressurized fluid within an accumulator, and sensing a pressure of fluid in the accumulator.
- the method may additionally include detecting a stall condition of the fluid actuator, and selectively charging or discharging the accumulator during the stall condition based on the pressure of the accumulated fluid.
- FIG. 1 is a diagrammatic illustration of an exemplary disclosed machine operating at a worksite with a haul vehicle
- FIG. 2 is a schematic illustration of an exemplary disclosed hydraulic control system that may be used with the machine of FIG. 1 ;
- FIG. 3 is an exemplary disclosed control map that may be used by the hydraulic control system of FIG. 2 ;
- FIG. 4 is a flowchart depicting an exemplary disclosed method that may be performed by the hydraulic control system of FIG. 2 .
- FIG. 1 illustrates an exemplary machine 10 having multiple systems and components that cooperate to excavate and load earthen material onto a nearby haul vehicle 12 .
- machine 10 is a hydraulic excavator. It is contemplated, however, that machine 10 could alternatively embody another swing-type excavation or material handling machine, such as a backhoe, a front shovel, a dragline excavator, or another similar machine.
- Machine 10 may include, among other things, an implement system 14 configured to move a work tool 16 between a dig location 18 within a trench or at a pile, and a dump location 20 , for example over haul vehicle 12 .
- Machine 10 may also include an operator station 22 for manual control of implement system 14 . It is contemplated that machine 10 may perform operations other than truck loading, if desired, such as craning, trenching, and material handling.
- Implement system 14 may include a linkage structure acted on by fluid actuators to move work tool 16 .
- implement system 14 may include a boom 24 that is vertically pivotal relative to a work surface 26 by a pair of adjacent, double-acting, hydraulic cylinders 28 (only one shown in FIG. 1 ).
- Implement system 14 may also include a stick 30 that is vertically pivotal about a horizontal pivot axis 32 relative to boom 24 by a single, double-acting, hydraulic cylinder 36 .
- Implement system 14 may further include a single, double-acting, hydraulic cylinder 38 that is operatively connected to work tool 16 to tilt work tool 16 vertically about a horizontal pivot axis 40 relative to stick 30 .
- Boom 24 may be pivotally connected to a frame 42 of machine 10 , while frame 42 may be pivotally connected to an undercarriage member 44 and swung about a vertical axis 46 by a swing motor 49 .
- Stick 30 may pivotally connect work tool 16 to boom 24 by way of pivot axes 32 and 40 . It is contemplated that a greater or lesser number of fluid actuators may be included within implement system 14 and connected in a manner other than described above, if desired.
- Work tool 16 may include any device used to perform a particular task such as, for example, a bucket, a fork arrangement, a blade, a shovel, a crusher, a shear, a grapple, a grapple bucket, a magnet, or any other task-performing device known in the art.
- work tool 16 may alternatively or additionally rotate, slide, extend, open and close, or move in another manner known in the art.
- Operator station 22 may be configured to receive input from a machine operator indicative of a desired work tool movement.
- operator station 22 may include one or more input devices 48 embodied, for example, as single or multi-axis joysticks located proximal an operator seat (not shown).
- Input devices 48 may be proportional-type controllers configured to position and/or orient work tool 16 by producing work tool position signals that are indicative of a desired work tool speed and/or force in a particular direction.
- the position signals may be used to actuate any one or more of hydraulic cylinders 28 , 36 , 38 and/or swing motor 49 .
- different input devices may alternatively or additionally be included within operator station 22 such as, for example, wheels, knobs, push-pull devices, switches, pedals, and other operator input devices known in the art.
- machine 10 may include a hydraulic control system 50 having a plurality of fluid components that cooperate to move implement system 14 (referring to FIG. 1 ).
- hydraulic control system 50 may include a first circuit 52 associated with swing motor 49 , and at least a second circuit 54 associated with hydraulic cylinders 28 , 36 , and 38 .
- First circuit 52 may include, among other things, a swing control valve 56 connected to regulate a flow of pressurized fluid from a pump 58 to swing motor 49 and from swing motor 49 to a low-pressure tank 60 to cause a swinging movement of work tool 16 about axis 46 (referring to FIG. 1 ) in accordance with an operator request received via input device 48 .
- Second circuit 54 may include similar control valves, for example a boom control valve (not shown), a stick control valve (not shown), a tool control valve (not shown), a travel control valve (not shown), and/or an auxiliary control valve connected in parallel to receive pressurized fluid from pump 58 and to discharge waste fluid to tank 60 , thereby regulating the corresponding actuators (e.g., hydraulic cylinders 28 , 36 , and 38 ).
- a boom control valve not shown
- a stick control valve not shown
- a tool control valve not shown
- a travel control valve not shown
- auxiliary control valve connected in parallel to receive pressurized fluid from pump 58 and to discharge waste fluid to tank 60 , thereby regulating the corresponding actuators (e.g., hydraulic cylinders 28 , 36 , and 38 ).
- Swing motor 49 may include a housing 62 at least partially forming a first and a second chamber (not shown) located to either side of an impeller 64 .
- first chamber is connected to an output of pump 58 (e.g., via a first chamber passage 66 formed within housing 62 ) and the second chamber is connected to tank 60 (e.g., via a second chamber passage 68 formed within housing 62 )
- impeller 64 may be driven to rotate in a first direction (shown in FIG. 2 ).
- impeller 64 may be driven to rotate in an opposite direction (not shown).
- the flow rate of fluid through impeller 64 may relate to a rotational speed of swing motor 49
- a pressure differential across impeller 64 may relate to an output torque thereof.
- Swing motor 49 may include built-in makeup and relief functionality.
- a makeup passage 70 and a relief passage 72 may be formed within housing 62 , between first chamber passage 66 and second chamber passage 68 .
- a pair of opposing check valves 74 and a pair of opposing relief valves 76 may be disposed within makeup and relief passages 70 , 72 , respectively.
- a low-pressure passage 78 may be connected to each of makeup and relief passages 70 , 72 at locations between check valves 74 and between relief valves 76 . Based on a pressure differential between low-pressure passage 78 and first and second chamber passages 66 , 68 , one of check valves 74 may open to allow fluid from low-pressure passage 78 into the lower-pressure one of the first and second chambers.
- one of relief valves 76 may open to allow fluid from the higher-pressure one of the first and second chambers into low-pressure passage 78 .
- a significant pressure differential may generally exist between the first and second chambers during a swinging movement of implement system 14 .
- Pump 58 may be configured to draw fluid from tank 60 via an inlet passage 80 , pressurize the fluid to a desired level, and discharge the fluid to first and second circuits 52 , 54 via a discharge passage 82 .
- a check valve 83 may be disposed within discharge passage 82 , if desired, to provide for a unidirectional flow of pressurized fluid from pump 58 into first and second circuits 52 , 54 .
- Pump 58 may embody, for example, a variable displacement pump (shown in FIG. 2 ), a fixed displacement pump, or another source known in the art.
- Pump 58 may be drivably connected to a power source (not shown) of machine 10 by, for example, a countershaft (not shown), a belt (not shown), an electrical circuit (not shown), or in another suitable manner.
- pump 58 may be indirectly connected to the power source of machine 10 via a torque converter, a reduction gear box, an electrical circuit, or in any other suitable manner.
- Pump 58 may produce a stream of pressurized fluid having a pressure level and/or a flow rate determined, at least in part, by demands of the actuators within first and second circuits 52 , 54 that correspond with operator requested movements.
- Discharge passage 82 may be connected within first circuit 52 to first and second chamber passages 66 , 68 via swing control valve 56 and first and second chamber conduits 84 , 86 , respectively, which extend between swing control valve 56 and swing motor 49 .
- Tank 60 may constitute a reservoir configured to hold a low-pressure supply of fluid.
- the fluid may include, for example, a dedicated hydraulic oil, an engine lubrication oil, a transmission lubrication oil, or any other fluid known in the art.
- One or more hydraulic systems within machine 10 may draw fluid from and return fluid to tank 60 .
- hydraulic control system 50 may be connected to multiple separate fluid tanks or to a single tank, as desired.
- Tank 60 may be fluidly connected to swing control valve 56 via a drain passage 88 , and to first and second chamber passages 66 , 68 via swing control valve 56 and first and second chamber conduits 84 , 86 , respectively.
- Tank 60 may also be connected to low-pressure passage 78 .
- a check valve 90 may be disposed within drain passage 88 , if desired, to promote a unidirectional flow of fluid into tank 60 .
- Swing control valve 56 may have elements that are movable to control the rotation of swing motor 49 and corresponding swinging motion of implement system 14 .
- swing control valve 56 may include a first chamber supply element 92 , a first chamber drain element 94 , a second chamber supply element 96 , and a second chamber drain element 98 all disposed within a common block or housing 97 .
- the first and second chamber supply elements 92 , 96 may be connected in parallel with discharge passage 82 to regulate filling of their respective chambers with fluid from pump 58
- the first and second chamber drain elements 94 , 98 may be connected in parallel with drain passage 88 to regulate draining of the respective chambers of fluid.
- a makeup valve 99 for example a check valve, may be disposed between an outlet of first chamber drain element 94 and first chamber conduit 84 and between an outlet of second chamber drain element 98 and second chamber conduit 86 .
- first chamber supply element 92 may be shifted to allow pressurized fluid from pump 58 to enter the first chamber of swing motor 49 via discharge passage 82 and first chamber conduit 84
- second chamber drain element 98 may be shifted to allow fluid from the second chamber of swing motor 49 to drain to tank 60 via second chamber conduit 86 and drain passage 88
- second chamber supply element 96 may be shifted to communicate the second chamber of swing motor 49 with pressurized fluid from pump 58
- first chamber drain element 94 may be shifted to allow draining of fluid from the first chamber of swing motor 49 to tank 60 .
- both the supply and drain functions of swing control valve 56 may alternatively be performed by a single valve element associated with the first chamber and a single valve element associated with the second chamber, or by a single valve element associated with both the first and second chambers, if desired.
- Supply and drain elements 92 - 98 of swing control valve 56 may be solenoid-movable against a spring bias in response to a flow rate and/or position command issued by a controller 100 .
- swing motor 49 may rotate at a velocity that corresponds with the flow rate of fluid into and out of the first and second chambers and with a torque that corresponds with a pressure differential across impeller 64 .
- a command based on an assumed or measured pressure drop may be sent to the solenoids (not shown) of supply and drain elements 92 - 98 that causes them to open an amount corresponding to the necessary fluid flow rates and/or pressure differential at swing motor 49 .
- This command may be in the form of a flow rate command or a valve element position command that is issued by controller 100 .
- Controller 100 may be in communication with the different components of hydraulic control system 50 to regulate operations of machine 10 .
- controller 100 may be in communication with the elements of swing control valve 56 in first circuit 52 and with the elements of control valves (not shown) associated with second circuit 54 .
- controller 100 may be configured to selectively activate the different control valves in a coordinated manner to efficiently carry out operator requested movements of implement system 14 .
- Controller 100 may include a memory, a secondary storage device, a clock, and one or more processors that cooperate to accomplish a task consistent with the present disclosure. Numerous commercially available microprocessors can be configured to perform the functions of controller 100 . It should be appreciated that controller 100 could readily embody a general machine controller capable of controlling numerous other functions of machine 10 . Various known circuits may be associated with controller 100 , including signal-conditioning circuitry, communication circuitry, and other appropriate circuitry. It should also be appreciated that controller 100 may include one or more of an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a computer system, and a logic circuit configured to allow controller 100 to function in accordance with the present disclosure.
- ASIC application-specific integrated circuit
- FPGA field-programmable gate array
- the operational parameters monitored by controller 100 may include a pressure of fluid within first and/or second circuits 52 , 54 .
- one or more pressure sensors 102 may be strategically located within first chamber and/or second chamber conduits 84 , 86 to sense a pressure of the respective passages and generate a corresponding signal indicative of the pressure directed to controller 100 . It is contemplated that any number of pressure sensors 102 may be placed in any location within first and/or second circuits 52 , 54 , as desired. It is further contemplated that other operational parameters such as, for example, speeds, temperatures, viscosities, densities, etc. may also or alternatively be monitored and used to regulate operation of hydraulic control system 50 , if desired.
- Hydraulic control system 50 may be fitted with an energy recovery arrangement 104 that is in communication with at least first circuit 52 and configured to selectively extract and recover energy from waste fluid that is discharged from swing motor 49 .
- Energy recovery arrangement (ERA) 104 may include, among other things, a recovery valve block (RVB) 106 that is fluidly connectable between pump 58 and swing motor 49 , a first accumulator 108 configured to selectively communicate with swing motor 49 via RVB 106 , and a second accumulator 110 also configured to selectively and directly communicate with swing motor 49 .
- RVB 106 may be fixedly and mechanically connectable to one or both of swing control valve 56 and swing motor 49 , for example directly to housing 62 and/or directly to housing 97 .
- RVB 106 may include an internal first passage 112 fluidly connectable to first chamber conduit 84 , and an internal second passage 114 fluidly connectable to second chamber conduit 86 .
- First accumulator 108 may be fluidly connected to RVB 106 via a conduit 116
- second accumulator 110 may be fluidly connectable to low-pressure and drain passages 78 and 88 , in parallel with tank 60 , via a conduit 118 .
- RVB 106 may house a selector valve 120 , a charge valve 122 associated with first accumulator 108 , and a discharge valve 124 associated with first accumulator 108 and disposed in parallel with charge valve 122 .
- Selector valve 120 may automatically fluidly communicate one of first and second passages 112 , 114 with charge and discharge valves 122 , 124 based on a pressure of first and second passages 112 , 114 .
- Charge and discharge valves 122 , 124 may be selectively movable in response to commands from controller 100 to fluidly communicate first accumulator 108 with selector valve 120 for fluid charging and discharging purposes.
- Selector valve 120 may be a pilot-operated, 2-position, 3-way valve that is automatically movable in response to fluid pressures in first and second passages 112 , 114 (i.e., in response to a fluid pressures within the first and second chambers of swing motor 49 ).
- selector valve 120 may include a valve element 126 that is movable from a first position (shown in FIG. 2 ) at which first passage 112 is fluidly connected to charge and discharge valves 122 , 124 via an internal passage 128 , toward a second position (not shown) at which second passage 114 is fluidly connected to charge and discharge valves 122 , 124 via passage 128 .
- first passage 112 When first passage 112 is fluidly connected to charge and discharge valves 122 , 124 via passage 128 , fluid flow through second passage 114 may be inhibited by selector valve 120 and vice versa.
- First and second pilot passages 130 , 132 may communicate fluid from first and second passages 112 , 114 to opposing ends of valve element 126 such that a higher-pressure one of first or second passages 112 , 114 may cause valve element 126 to move and fluidly connect the corresponding passage with charge and discharge valves 122 , 124 via passage 128 .
- Charge valve 122 may be a solenoid-operated, variable position, 2-way valve that is movable in response to a command from controller 100 to allow fluid from passage 128 to enter first accumulator 108 .
- charge valve 122 may include a valve element 134 that is movable from a first position (shown in FIG. 2 ) at which fluid flow from passage 128 into first accumulator 108 is inhibited, toward a second position (not shown) at which passage 128 is fluidly connected to first accumulator 108 .
- valve element 134 When valve element 134 is away from the first position (i.e., in the second position or in an intermediate position between the first and second positions) and a fluid pressure within passage 128 exceeds a fluid pressure within first accumulator 108 , fluid from passage 128 may fill (i.e., charge) first accumulator 108 .
- Valve element 134 may be spring-biased toward the first position and movable in response to a command from controller 100 to any position between the first and second positions to thereby vary a flow rate of fluid from passage 128 into first accumulator 108 .
- a check valve 136 may be disposed between charge valve 122 and first accumulator 108 to provide for a unidirectional flow of fluid into accumulator 108 via charge valve 122 .
- Discharge valve 124 may be substantially identical to charge valve 122 in composition, and movable in response to a command from controller 100 to allow fluid from first accumulator 108 to enter passage 128 (i.e., to discharge).
- discharge valve 124 may include a valve element 138 that is movable from a first position (not shown) at which fluid flow from first accumulator 108 into passage 128 is inhibited, toward a second position (shown in FIG. 2 ) at which first accumulator 108 is fluidly connected to passage 128 .
- valve element 138 When valve element 138 is away from the first position (i.e., in the second position or in an intermediate position between the first and second positions) and a fluid pressure within first accumulator 108 exceeds a fluid pressure within passage 128 , fluid from first accumulator 108 may flow into passage 128 .
- Valve element 138 may be spring-biased toward the first position and movable in response to a command from controller 100 to any position between the first and second positions to thereby vary a flow rate of fluid from first accumulator 108 into passage 128 .
- a check valve 140 may be disposed between first accumulator 108 and discharge valve 124 to provide for a unidirectional flow of fluid from accumulator 108 into passage 128 via discharge valve 124 .
- An additional pressure sensor 102 may be associated with first accumulator 108 and configured to generate signals indicative of a pressure of fluid within first accumulator 108 , if desired.
- the additional pressure sensor 102 may be disposed between first accumulator 108 and discharge valve 124 . It is contemplated, however, that the additional pressure sensor 102 may alternatively be disposed between first accumulator 108 and charge valve 122 or directly connected to first accumulator 108 , if desired. Signals from this additional pressure sensor 102 may be directed to controller 100 for use in regulating operation of charge and/or discharge valves 122 , 124 .
- First and second accumulators 108 , 110 may each embody pressure vessels filled with a compressible gas that are configured to store pressurized fluid for future use by swing motor 49 .
- the compressible gas may include, for example, nitrogen, argon, helium, or another appropriate compressible gas.
- the fluid may flow into accumulators 108 , 110 . Because the gas therein is compressible, it may act like a spring and compress as the fluid flows into first and second accumulators 108 , 110 .
- first and second accumulators 108 , 110 may alternatively embody membrane/spring-biased or bladder types of accumulators, if desired.
- first accumulator 108 may be a larger (i.e., about 5-20 times larger) and higher-pressure (i.e., about 5-60 times higher-pressure) accumulator, as compared to second accumulator 110 .
- first accumulator 108 may be configured to accumulate up to about 50-100 L of fluid having a pressure in the range of about 260-315 bar
- second accumulator 110 may be configured to accumulate up to about 10 L of fluid having a pressure in the range of about 5-30 bar.
- first accumulator 108 may be used primarily to assist the motion of swing motor 49 and to improve machine efficiencies, while second accumulator may be used primarily as a makeup accumulator to help reduce a likelihood of voiding at swing motor 49 . It is contemplated, however, that other volumes and pressures may be accommodated by first and/or second accumulators 108 , 110 , if desired.
- Controller 100 may be configured to selectively cause first accumulator 108 to charge and discharge, thereby improving performance of machine 10 .
- a typical swinging motion of implement system 14 instituted by swing motor 49 may consist of segments of time during which swing motor 49 is accelerating a swinging movement of implement system 14 , and segments of time during which swing motor 49 is decelerating the swinging movement of implement system 14 .
- the acceleration segments may require significant energy from swing motor 49 that is conventionally realized by way of pressurized fluid supplied to swing motor 49 by pump 58 , while the deceleration segments may produce significant energy in the form of pressurized fluid that is conventionally wasted through discharge to tank 60 .
- Both the acceleration and the deceleration segments may require swing motor 49 to convert significant amounts of hydraulic energy to swing kinetic energy, and vice versa.
- the fluid passing through swing motor 49 during deceleration still contains a large amount of energy.
- the fluid passing through swing motor 49 may be pressurized during deceleration as a result of restrictions to the flow of the fluid exiting swing motor 49 . If the fluid passing through swing motor 49 is selectively collected within first accumulator 108 during the deceleration segments, this energy can then be returned to (i.e., discharged) and reused by swing motor 49 during the ensuing acceleration segments.
- Swing motor 49 can be assisted during the acceleration segments by selectively causing first accumulator 108 to discharge pressurized fluid into the higher-pressure chamber of swing motor 49 (via discharge valve 124 , passage 128 , selector valve 120 , and the appropriate one of first and second chamber conduits 84 , 86 ), alone or together with high-pressure fluid from pump 58 , thereby propelling swing motor 49 at the same or greater rate with less pump power than otherwise possible via pump 58 alone.
- Swing motor 49 can be assisted during the deceleration segments by selectively causing first accumulator 108 to charge with fluid exiting swing motor 49 , thereby providing additional resistance to the motion of swing motor 49 and lowering a restriction and cooling requirement of the fluid exiting swing motor 49 .
- controller 100 may be configured to selectively control charging of first accumulator 108 with fluid exiting pump 58 , as opposed to fluid exiting swing motor 49 . That is, during a peak-shaving or economy mode of operation, controller 100 may be configured to cause accumulator 108 to charge with fluid exiting pump 58 (e.g., via control valve 56 , the appropriate one of first and second chamber conduits 84 , 86 , selector valve 120 , passage 128 , and charge valve 122 ) when pump 58 has excess capacity (i.e., a capacity greater than required by circuits 52 , 54 to move work tool 16 as requested by the operator). Then, during times when pump 58 has insufficient capacity to adequately power swing motor 49 , the high-pressure fluid previously collected from pump 58 within first accumulator 108 may be discharged in the manner described above to assist swing motor 49 .
- Controller 100 may be configured to regulate the charging and discharging of first accumulator 108 based on a current or ongoing segment of the excavation, material handling, or other work cycle of machine 10 .
- controller 100 may be configured to partition a typical work cycle performed by machine 10 into a plurality of segments.
- a typical work cycle may be partitioned, for example, into a dig segment, a swing-to-dump acceleration segment, a swing-to-dump deceleration segment, a dump segment, a swing-to-dig acceleration segment, and a swing-to-dig deceleration segment, as will be described in more detail below.
- controller 100 may selectively cause first accumulator 108 to charge or discharge, thereby assisting swing motor 49 during the acceleration and deceleration segments.
- One or more maps and/or dynamic elements relating signals from sensor(s) 141 to the different segments of the excavation work cycle may be stored within the memory of controller 100 .
- Each of these maps may include a collection of data in the form of tables, graphs, and/or equations.
- the dynamic elements may include integrators, filters, rate limiters, and delay elements.
- threshold speeds, cylinder pressures, and/or operator input (i.e., lever position) associated with the start and/or end of one or more of the segments may be stored within the maps.
- threshold forces and/or actuator positions associated with the start and/or end of one or more of the segments may be stored within the maps.
- Controller 100 may be configured to reference the signals from sensor(s) 141 with the maps and filters stored in memory to determine the segment of the excavation work cycle currently being executed, and then regulate the charging and discharging of first accumulator 108 accordingly. Controller 100 may allow the operator of machine 10 to directly modify these maps and/or to select specific maps from available relationship maps stored in the memory of controller 100 to affect segment partitioning and accumulator control, as desired. It is contemplated that the maps may additionally or alternatively be automatically selectable based on modes of machine operation, if desired.
- Sensor(s) 141 may be associated with the generally horizontal swinging motion of work tool 16 imparted by swing motor 49 (i.e., the motion of frame 42 relative to undercarriage member 44 ).
- sensor 141 may embody a rotational position or speed sensor associated with the operation of swing motor 49 , an angular position or speed sensor associated with the pivot connection between frame 42 and undercarriage member 44 , a local or global coordinate position or speed sensor associated with any linkage member connecting work tool 16 to undercarriage member 44 or with work tool 16 itself, a displacement sensor associated with movement of operator input device 48 , or any other type of sensor known in the art that may generate a signal indicative of a swing position, speed, force, or other swing-related parameter of machine 10 .
- the signal generated by sensor(s) 141 may be sent to and recorded by controller 100 during each excavation work cycle. It is contemplated that controller 100 may derive a swing speed based on a position signal from sensor 141 and an elapsed period of time, if desired.
- sensor(s) 141 may be associated with the vertical pivoting motion of work tool 16 imparted by hydraulic cylinders 28 (i.e., associated with the lifting and lowering motions of boom 24 relative to frame 42 ).
- sensor 141 may be an angular position or speed sensor associated with a pivot joint between boom 24 and frame 42 , a displacement sensor associated with hydraulic cylinders 28 , a local or global coordinate position or speed sensor associated with any linkage member connecting work tool 16 to frame 42 or with work tool 16 itself, a displacement sensor associated with movement of operator input device 48 , or any other type of sensor known in the art that may generate a signal indicative of a pivoting position or speed of boom 24 .
- controller 100 may derive a pivot speed based on a position signal from sensor 141 and an elapsed period of time, if desired.
- sensor(s) 141 may be associated with the tilting force of work tool 16 imparted by hydraulic cylinder 38 .
- sensor 141 may be a pressure sensor associated with one or more chambers within hydraulic cylinder 38 or any other type of sensor known in the art that may generate a signal indicative of a tilting force of machine 10 generated during a dig and dump operation of work tool 16 .
- an exemplary curve 142 may represent a swing speed signal generated by sensor(s) 141 relative to time throughout each segment of an excavation work cycle, for example throughout a work cycle associated with 90° truck loading.
- the swing speed may typically be about zero (i.e., machine 10 may generally not swing during a digging operation).
- machine 10 may generally be controlled to swing work tool 16 toward the waiting haul vehicle 12 (referring to FIG. 1 ). As such, the swing speed of machine 10 may begin to increase near the end of the dig segment.
- the swing speed may accelerate to a maximum when work tool 16 is about midway between dig location 18 and dump location 20 , and then decelerate toward the end of the swing-to-dump segment.
- the swing speed may typically be about zero (i.e., machine 10 may generally not swing during a dumping operation).
- machine 10 may generally be controlled to swing work tool 16 back toward dig location 18 (referring to FIG. 1 ). As such, the swing speed of machine 10 may increase near the end of the dump segment.
- Controller 100 may partition a current excavation work cycle into the six segments described above based on signals received from sensor(s) 141 and the maps and filters stored in memory, based on swing speeds, tilt forces, and/or operator input recorded for a previous excavation work cycle, or in any other manner known in the art.
- Controller 100 may selectively cause first accumulator 108 to charge and to discharge based on the current or ongoing segment of the excavation work cycle.
- a chart portion 144 (i.e., the lower portion) of FIG. 3 illustrates 6 different modes of operations during which the excavation cycle can be completed, together with an indication as to when first accumulator 108 is controlled to charge with pressurized fluid (represented by “C”) or to discharge pressurized fluid (represented by “D”) relative to the segments of each excavation work cycle.
- First accumulator 108 can be controlled to charge with pressurized fluid by moving valve element 134 of charge valve 122 to the second or flow-passing position when the pressure within passage 128 is greater than the pressure within first accumulator 108 .
- First accumulator 108 can be controlled to discharge pressurized fluid by moving valve element 138 of discharge valve 124 to the second or flow-passing position when the pressure within first accumulator 108 is greater than the pressure within passage 128 .
- controller 100 may inhibit first accumulator 108 from receiving or discharging fluid during the dig and dump segments of all of the modes of operation (i.e., controller 100 may maintain valve elements 134 and 138 in the flow-blocking first positions during the dig and dump segments). Controller 100 may inhibit charging and discharging during the dig and dump segments, as no or little or no swinging motion is required during completion of these portions of the excavation work cycle. Second, the number of segments during which controller 100 causes first accumulator 108 to receive fluid may be greater than the number of segments during which controller 100 causes first accumulator 108 to discharge fluid for a majority of the modes (e.g., for modes 2-6).
- Controller 100 may generally cause first accumulator 108 to charge more often than discharge, because the amount of charge energy available at a sufficiently high pressure (i.e., at a pressure greater than the threshold pressure of first accumulator 108 ) may be less than an amount of energy required during movement of implement system 14 .
- the number of segments during which controller 100 causes first accumulator 108 to discharge fluid may never be greater than the number of segments during which controller 100 causes first accumulator 108 to receive fluid for all modes.
- controller 100 may cause first accumulator 108 to discharge fluid during only a swing-to-dig or a swing-to-dump acceleration segment for all modes. Discharge during any other segment of the excavation cycle may only serve to reduce machine efficiency.
- controller 100 may cause first accumulator 108 to receive fluid during only a swing-to-dig or swing-to-dump deceleration segment for a majority of the modes of operation (e.g., for modes 1-4).
- Mode 1 may correspond with a swing-intensive operation where a significant amount of swing energy is available for storage by first accumulator 108 .
- An exemplary swing-intensive operation may include a 150° (or greater) swing operation, such as the truck loading example shown in FIG. 1 , material handling (e.g., using a grapple or magnet), hopper feeding from a nearby pile, or another operation where an operator of machine 10 typically requests harsh stop-and-go commands.
- controller 100 may be configured to cause first accumulator 108 to discharge fluid to swing motor 49 during the swing-to-dump acceleration segment, receive fluid from swing motor 49 during the swing-to-dump deceleration segment, discharge fluid to swing motor 49 during the swing-to-dig acceleration segment, and receive fluid from swing motor 49 during the swing-to-dig deceleration segment.
- Controller 100 may be instructed by the operator of machine 10 that the first mode of operation is currently in effect (e.g., that truck loading is being performed) or, alternatively, controller 100 may automatically recognize operation in the first mode based on performance of machine 10 monitored via sensor(s) 141 .
- controller 100 could monitor swing angle of implement system 14 between stopping positions (i.e., between dig and dump locations 18 , 20 ) and, when the swing angle is repeatedly greater than a threshold angle, for instance greater than about 150°, controller 100 may determine that the first mode of operation is in effect.
- manipulation of input device 48 could be monitored via sensor(s) 141 to detect “harsh” inputs indicative of mode 1 operation.
- controller 100 may responsively determine that the first mode of operation is in effect.
- controller 100 may determine that the first mode of operation is in effect based on a cycle and/or value of pressures within accumulator 108 , for example when a threshold pressure is repetitively reached.
- the threshold pressure may be about 75% of a maximum pressure.
- Modes 2-4 may correspond generally with swing operations where only a limited amount of swing energy is available for storage by first accumulator 108 .
- Exemplary swing operations having a limited amount of energy may include 90° truck loading, 45° trenching, tamping, or slow and smooth craning. During these operations, fluid energy may need to be accumulated from two or more segments of the excavation work cycle before significant discharge of the accumulated energy is possible. It should be noted that, although mode 4 is shown as allowing two segments of discharge from first accumulator 108 , one segment (e.g., the swing-to-dump segment) may only allow for a partial discharge of accumulated energy.
- modes 2-4 may be triggered manually by an operator of machine 10 or, alternatively, automatically triggered based on performance of machine 10 as monitored via sensor(s) 141 .
- controller 100 may determine that one of modes 2-4 is in effect.
- controller 100 may determine that modes 2-4 are in effect based on operator requested boom movement less than a threshold amount (e.g., less than about 80% lever command for mode 2 or 4), and/or work tool tilting less than a threshold amount (e.g., less than about 80% lever command for mode 3 or 4).
- controller 100 may cause first accumulator 108 to discharge fluid to swing motor 49 during only the swing-to-dump acceleration segment, receive fluid from swing motor 49 during the swing-to-dump deceleration segment, and receive fluid from swing motor 49 during the swing-to-dig deceleration segment.
- controller 100 may cause first accumulator 108 to receive fluid from swing motor 49 during the swing-to-dump deceleration segment, discharge fluid to swing motor 49 during only the swing-to-dig acceleration segment, and receive fluid from swing motor 49 during the swing-to-dig deceleration segment.
- controller 100 may cause first accumulator 108 to discharge only a portion of previously-recovered fluid to swing motor 49 during the swing-to-dump acceleration segment, receive fluid from swing motor 49 during the swing-to-dump deceleration segment, discharge fluid to swing motor 49 during the swing-to-dig acceleration segment, and receive fluid from swing motor 49 during the swing-to-dig deceleration segment.
- Modes 5 and 6 may be known as economy or peak-shaving modes, where excess fluid energy during one segment of the excavation work cycle is generated by pump 58 (fluid energy in excess of an amount required to adequately drive swing motor 49 according to operator requests) and stored for use during another segment when less than adequate fluid energy may be available for a desired swinging operation.
- controller 100 may cause first accumulator 108 to charge with pressurized fluid from pump 58 during a swing acceleration segment, for example during the swing-to-dump or swing-to-dig acceleration segments, when the excess fluid energy is available. Controller 100 may then cause first accumulator 108 to discharge the accumulated fluid during another acceleration segment when less than adequate energy is available.
- controller 100 may cause first accumulator 108 to discharge fluid to swing motor 49 during only the swing-to-dump acceleration segment, receive fluid from swing motor 49 during the swing-to-dump deceleration segment, receive fluid from pump 58 during the swing-to-dig acceleration segment, and receive fluid from swing motor 49 during the swing-to-dig deceleration segment, for a total of three charging segments and one discharging segment.
- controller 100 may cause first accumulator 108 to receive fluid from pump 58 during the swing-to-dump acceleration segment, receive fluid from swing motor 49 during the swing-to-dump deceleration segment, discharge fluid to swing motor 49 during the swing-to-dig acceleration segment, and receive fluid from swing motor 49 during the swing-to-dig deceleration segment.
- controller 100 may be limited during the charging and discharging of first accumulator 108 by fluid pressures within first chamber conduit 84 , second chamber conduit 86 , and first accumulator 108 . That is, even though a particular segment in the work cycle of machine 10 during a particular mode of operation may call for charging or discharging of first accumulator 108 , controller 100 may only be allowed to implement the action when the related pressures have corresponding values. For example, if sensors 102 indicate that a pressure of fluid within first accumulator 108 is below a pressure of fluid within first chamber conduit 84 , controller 100 may not be allowed to initiate discharging of first accumulator 108 into first chamber conduit 84 .
- controller 100 may not be allowed to initiate charging of first accumulator 108 with fluid from second chamber conduit 86 . Not only could the exemplary processes be difficult (if not impossible) to implement at particular times when the related pressures are inappropriate, but an attempt to implement the processes could result in undesired machine performance.
- second accumulator 110 may be configured to charge with fluid exiting swing motor 49 any time that first accumulator 108 is discharging fluid to swing motor 49 .
- second accumulator 110 may be configured to discharge to swing motor 49 any time that first accumulator 108 is charging with fluid from swing motor 49 .
- second accumulator 110 may discharge fluid any time a pressure within low-pressure passage 78 falls below the pressure of fluid within second accumulator 110 . Accordingly, the discharge of fluid from second accumulator 110 into first circuit 52 may not be directly regulated via controller 100 . However, because second accumulator 110 may charge with fluid from first circuit 52 whenever the pressure within drain passage 88 exceeds the pressure of fluid within second accumulator 110 , and because control valve 56 may affect the pressure within drain passage 88 , controller 100 may have some control over the charging of second accumulator 110 with fluid from first circuit 52 via control valve 56 .
- first and second accumulators 108 , 110 may simultaneously charge with pressurized fluid. These situations may correspond, for example, with operation in the peak-shaving modes (i.e., in modes 5 and 6.).
- second accumulator 110 may charge with pressurized fluid at the same time that pump 58 is providing pressurized fluid to both swing motor 49 and to first accumulator 108 (e.g., during the swing-to-dig acceleration segment of mode 5 and/or during the swing-to-dump acceleration segment of mode 6).
- the fluid exiting pump 58 may be directed into first accumulator 108
- the fluid exiting swing motor 49 may be directed into second accumulator 110 .
- Second accumulator 110 may also be charged via second circuit 54 , if desired.
- any time waste fluid from second circuit 54 i.e., fluid draining from second circuit 54 to tank 60
- the waste fluid may be collected within second accumulator 110 .
- pressurized fluid within second accumulator 110 may be selectively discharged into second circuit 54 when the pressure within second circuit 54 falls below the pressure of fluid collected within second accumulator 110 .
- swing motor 49 may stall.
- work tool 16 , boom 24 , stick 30 , and/or frame 42 may engage an immovable object (e.g., a side of a trench, a boulder, another machine, etc.).
- pump 58 may still be pressurizing fluid and directing fluid to a particular chamber of swing motor 49 according to operator demand (i.e., according to a displacement position of input device 48 ). While some of this fluid may find leak paths through swing motor 49 , the majority of the fluid will be forced to spill over relief valves 76 as the pressure of first circuit 52 rises during the stall.
- controller 100 may be configured to selectively connect RVB 106 with swing motor 49 during a stall event to either charge or discharge first accumulator 108 while simultaneously altering operation of pump 58 to try and recuperate some of the otherwise wasted energy.
- FIG. 4 illustrates an exemplary method used by controller 100 for this purpose. FIG. 4 will be discussed in more detail below to further illustrate the disclosed concepts.
- the disclosed hydraulic control system may be applicable to any excavation machine that performs a substantially repetitive work cycle, which involves swinging movements of a work tool.
- the disclosed hydraulic control system may help to improve machine performance and efficiency by assisting swinging acceleration and deceleration of the work tool with an accumulator during different segments of the work cycle.
- the unique method used by the disclosed hydraulic control system may help ensure energy recuperation even during a stall event. Operation of the disclosed hydraulic control system will now be described in detail with reference to FIG. 4 .
- controller 100 may monitor different operating parameters of hydraulic control system 50 during operation of machine 10 .
- controller 100 may monitor a pressure of fluid at swing motor 49 , a lever displacement position of input device 48 , and a velocity of swing motor 49 (Step 300 ). Based on this information, controller 100 may determine if swing motor 49 is experiencing a stall condition (Step 310 ).
- Controller 100 may determine that swing motor 49 is experiencing a stall condition when input device 48 is displaced at least a minimum amount indicating an operator's desire for swing motor 49 to rotate, when a significant pressure differential exists across swing motor 49 (i.e., a pressure differential greater than a predetermined amount indicating that significant force is being generated by swing motor 49 ), and when swing motor 49 is moving too slow, if at all (i.e., moving at a velocity less than a minimum threshold amount).
- the minimum displacement amount of input device 48 may be a displacement of about 10-30% of a maximum displacement; the predetermined pressure differential may be a pressure differential greater than about 200-300 bar; and the minimum threshold velocity may be about 0.1-0.5 rpm. It is contemplated, however, that other ways of determining and/or other values used to determine the stalled condition status of swing motor 49 may alternatively be utilized, if desired. When swing motor 49 is not experiencing the stalled condition, control may return to step 300 .
- controller 100 may compare a pressure of first accumulator 108 to one or more threshold pressures (Step 320 ).
- two different pressure thresholds may be used, including a first pressure threshold and a second pressure threshold.
- the first pressure threshold may be about 280 bar and the second pressure threshold may be about 290 bar.
- controller 100 may be configured to close the appropriate first or second chamber supply valve 92 or 96 (depending on the desired rotational direction of swing motor 49 ), de-stroke pump 58 , and open discharge valve 124 (Step 330 ).
- first accumulator 108 may have a sufficient store of pressurized fluid and this store may be used as the sole source to drive swing motor 49 , thereby saving the otherwise wasted energy that would have been consumed by pump 58 .
- Control may proceed from step 330 to step 300 . It should be noted that, once controller 100 begins discharge of first accumulator 108 during a stall event, discharge may continue until swing motor 49 is no longer stalled or until the pressure of first accumulator 108 falls below the first pressure threshold.
- controller 100 may be configured to open or maintain open the appropriate first or second chamber supply valve 92 or 96 (depending on the desired rotational direction of swing motor 49 ), reduce a displacement of pump 58 , and open charge valve 122 (Step 340 ).
- first accumulator 108 may have capacity to store additional pressurized fluid, and the reduced output of pump 58 , instead of being wasted could be directed into and stored within first accumulator 108 .
- Control may proceed from step 340 to step 300 . It should be noted that, once controller 100 begins charging of first accumulator 108 during a stall event, charging may continue until swing motor 49 is no longer stalled or until the pressure of first accumulator 108 rises above the second pressure threshold.
- hydraulic control system 50 may utilize a high-pressure accumulator and a low-pressure accumulator (i.e., first and second accumulators 108 , 110 ), a large amount of fluid discharged from swing motor 49 during acceleration segments of the excavation work cycle may be recovered. This double recovery of energy may help to increase the efficiency of machine 10 .
- second accumulator 110 may help to reduce the likelihood of voiding at swing motor 49 .
- the ability to adjust accumulator charging and discharging based on a current segment of the excavation work cycle and/or based on a current mode of operation may allow hydraulic control system 50 to tailor swing performance of machine 10 for particular applications, thereby enhancing machine performance and/or further improving machine efficiency.
- use of the disclosed method implemented by controller 100 during stall events i.e., during stall of swing motor 49 ) may further enhance machine efficiency.
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Abstract
Description
- This application is based on and claims the benefit of priority from U.S. Provisional Application No. 61/695,466 by Rustu CESUR et al., filed Aug. 31, 2012, the contents of which are expressly incorporated herein by reference.
- The present disclosure relates generally to a hydraulic control system and, more particularly, to a hydraulic control system having swing energy recovery.
- Swing-type excavation machines, for example hydraulic excavators and front shovels, require significant hydraulic pressure and flow to transfer material from a dig location to a dump location. These machines direct the high-pressure fluid from an engine-driven pump through a swing motor to accelerate a loaded work tool at the start of each swing, and then restrict the flow of fluid exiting the motor at the end of each swing to slow and stop the work tool.
- One problem associated with this type of hydraulic arrangement involves efficiency. In particular, the fluid exiting the swing motor at the end of each swing is under a relatively high pressure due to deceleration of the loaded work tool. Unless recovered, energy associated with the high-pressure fluid may be wasted. In addition, restriction of this high-pressure fluid exiting the swing motor at the end of each swing can result in heating of the fluid, which must be accommodated with an increased cooling capacity of the machine.
- One attempt to improve the efficiency of a swing-type machine is disclosed in U.S. Pat. No. 7,908,852 of Zhang et al. that issued on Mar. 22, 2011 (the '852 patent). The '852 patent discloses a hydraulic control system for a machine that includes an accumulator. The accumulator stores exit oil from a swing motor that has been pressurized by inertia torque applied on the moving swing motor by an upper structure of the machine. The pressurized oil in the accumulator is then selectively reused to accelerate the swing motor during a subsequent swing by supplying the accumulated oil back to the swing motor.
- Although the hydraulic control system of the '852 patent may help to improve efficiencies of a swing-type machine in some situations, it may still be less than optimal. In particular, during discharge of the accumulator described in the '852 patent, some pressurized fluid exiting the swing motor may still have useful energy that is wasted. In addition, there may be situations during operation of the hydraulic control system of the '852 patent, for example during deceleration and accumulator charging, when a pump output is unable to supply fluid at a rate sufficient to prevent cavitation in the swing motor. Further, the machine may operate differently under different conditions and in different situations, and the hydraulic control system of the '852 patent may not be configured to adapt control to these different conditions and situations. Finally, the '852 patent does not disclose operational control during a stall condition.
- The disclosed hydraulic control system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.
- One aspect of the present disclosure is directed to a hydraulic control system. The hydraulic control system may include a tank, a pump configured to draw fluid from the tank and pressurize the fluid, and a fluid actuator driven by a flow of pressurized fluid from the pump. The hydraulic control system may further include an accumulator configured to selectively receive pressurized fluid discharged from the fluid actuator and selectively supply pressurized fluid to the fluid actuator. The hydraulic control system may also include a pressure sensor configured to generate a signal indicative of a pressure of the accumulator, a charge valve configured to regulate fluid flow into the accumulator, a discharge valve configured to regulate fluid flow out of the accumulator, and a controller in communication with the control valve, the charge valve, and the discharge valve. The controller may be configured to detect stall of the fluid actuator, to make a comparison of the pressure of the accumulator with a threshold pressure, and to selectively move the charge valve to charge the accumulator or move the discharge valve to discharge the accumulator during the stall based on the comparison.
- In another aspect, the present disclosure is directed to method of operating a hydraulic control system. The method may include drawing fluid from a tank and pressurizing the fluid with a pump. The method may also include selectively directing pressurized fluid to a fluid actuator and from the fluid actuator to the tank to move the fluid actuator. The method may further include collecting pressurized fluid within an accumulator, and sensing a pressure of fluid in the accumulator. The method may additionally include detecting a stall condition of the fluid actuator, and selectively charging or discharging the accumulator during the stall condition based on the pressure of the accumulated fluid.
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FIG. 1 is a diagrammatic illustration of an exemplary disclosed machine operating at a worksite with a haul vehicle; -
FIG. 2 is a schematic illustration of an exemplary disclosed hydraulic control system that may be used with the machine ofFIG. 1 ; -
FIG. 3 is an exemplary disclosed control map that may be used by the hydraulic control system ofFIG. 2 ; and -
FIG. 4 is a flowchart depicting an exemplary disclosed method that may be performed by the hydraulic control system ofFIG. 2 . -
FIG. 1 illustrates anexemplary machine 10 having multiple systems and components that cooperate to excavate and load earthen material onto a nearbyhaul vehicle 12. In the depicted example,machine 10 is a hydraulic excavator. It is contemplated, however, thatmachine 10 could alternatively embody another swing-type excavation or material handling machine, such as a backhoe, a front shovel, a dragline excavator, or another similar machine.Machine 10 may include, among other things, animplement system 14 configured to move awork tool 16 between adig location 18 within a trench or at a pile, and adump location 20, for example overhaul vehicle 12. -
Machine 10 may also include anoperator station 22 for manual control ofimplement system 14. It is contemplated thatmachine 10 may perform operations other than truck loading, if desired, such as craning, trenching, and material handling. -
Implement system 14 may include a linkage structure acted on by fluid actuators to movework tool 16. Specifically,implement system 14 may include aboom 24 that is vertically pivotal relative to awork surface 26 by a pair of adjacent, double-acting, hydraulic cylinders 28 (only one shown inFIG. 1 ).Implement system 14 may also include astick 30 that is vertically pivotal about ahorizontal pivot axis 32 relative toboom 24 by a single, double-acting,hydraulic cylinder 36.Implement system 14 may further include a single, double-acting,hydraulic cylinder 38 that is operatively connected towork tool 16 totilt work tool 16 vertically about ahorizontal pivot axis 40 relative to stick 30.Boom 24 may be pivotally connected to aframe 42 ofmachine 10, whileframe 42 may be pivotally connected to anundercarriage member 44 and swung about avertical axis 46 by aswing motor 49.Stick 30 may pivotally connectwork tool 16 to boom 24 by way ofpivot axes system 14 and connected in a manner other than described above, if desired. - Numerous
different work tools 16 may be attachable to asingle machine 10 and controllable viaoperator station 22.Work tool 16 may include any device used to perform a particular task such as, for example, a bucket, a fork arrangement, a blade, a shovel, a crusher, a shear, a grapple, a grapple bucket, a magnet, or any other task-performing device known in the art. Although connected in the embodiment ofFIG. 1 to lift, swing, and tilt relative tomachine 10,work tool 16 may alternatively or additionally rotate, slide, extend, open and close, or move in another manner known in the art. -
Operator station 22 may be configured to receive input from a machine operator indicative of a desired work tool movement. Specifically,operator station 22 may include one ormore input devices 48 embodied, for example, as single or multi-axis joysticks located proximal an operator seat (not shown).Input devices 48 may be proportional-type controllers configured to position and/ororient work tool 16 by producing work tool position signals that are indicative of a desired work tool speed and/or force in a particular direction. The position signals may be used to actuate any one or more ofhydraulic cylinders swing motor 49. It is contemplated that different input devices may alternatively or additionally be included withinoperator station 22 such as, for example, wheels, knobs, push-pull devices, switches, pedals, and other operator input devices known in the art. - As illustrated in
FIG. 2 ,machine 10 may include ahydraulic control system 50 having a plurality of fluid components that cooperate to move implement system 14 (referring toFIG. 1 ). In particular,hydraulic control system 50 may include afirst circuit 52 associated withswing motor 49, and at least asecond circuit 54 associated withhydraulic cylinders First circuit 52 may include, among other things, aswing control valve 56 connected to regulate a flow of pressurized fluid from apump 58 to swingmotor 49 and fromswing motor 49 to a low-pressure tank 60 to cause a swinging movement ofwork tool 16 about axis 46 (referring toFIG. 1 ) in accordance with an operator request received viainput device 48.Second circuit 54 may include similar control valves, for example a boom control valve (not shown), a stick control valve (not shown), a tool control valve (not shown), a travel control valve (not shown), and/or an auxiliary control valve connected in parallel to receive pressurized fluid frompump 58 and to discharge waste fluid to tank 60, thereby regulating the corresponding actuators (e.g.,hydraulic cylinders -
Swing motor 49 may include ahousing 62 at least partially forming a first and a second chamber (not shown) located to either side of animpeller 64. When the first chamber is connected to an output of pump 58 (e.g., via afirst chamber passage 66 formed within housing 62) and the second chamber is connected to tank 60 (e.g., via asecond chamber passage 68 formed within housing 62),impeller 64 may be driven to rotate in a first direction (shown inFIG. 2 ). Conversely, when the first chamber is connected totank 60 viafirst chamber passage 66 and the second chamber is connected to pump 58 viasecond chamber passage 68,impeller 64 may be driven to rotate in an opposite direction (not shown). The flow rate of fluid throughimpeller 64 may relate to a rotational speed ofswing motor 49, while a pressure differential acrossimpeller 64 may relate to an output torque thereof. -
Swing motor 49 may include built-in makeup and relief functionality. In particular, amakeup passage 70 and a relief passage 72 may be formed withinhousing 62, betweenfirst chamber passage 66 andsecond chamber passage 68. A pair of opposingcheck valves 74 and a pair of opposingrelief valves 76 may be disposed within makeup andrelief passages 70, 72, respectively. A low-pressure passage 78 may be connected to each of makeup andrelief passages 70, 72 at locations betweencheck valves 74 and betweenrelief valves 76. Based on a pressure differential between low-pressure passage 78 and first andsecond chamber passages check valves 74 may open to allow fluid from low-pressure passage 78 into the lower-pressure one of the first and second chambers. Similarly, based on a pressure differential between first andsecond chamber passages pressure passage 78, one ofrelief valves 76 may open to allow fluid from the higher-pressure one of the first and second chambers into low-pressure passage 78. A significant pressure differential may generally exist between the first and second chambers during a swinging movement of implementsystem 14. -
Pump 58 may be configured to draw fluid fromtank 60 via aninlet passage 80, pressurize the fluid to a desired level, and discharge the fluid to first andsecond circuits discharge passage 82. Acheck valve 83 may be disposed withindischarge passage 82, if desired, to provide for a unidirectional flow of pressurized fluid frompump 58 into first andsecond circuits Pump 58 may embody, for example, a variable displacement pump (shown inFIG. 2 ), a fixed displacement pump, or another source known in the art.Pump 58 may be drivably connected to a power source (not shown) ofmachine 10 by, for example, a countershaft (not shown), a belt (not shown), an electrical circuit (not shown), or in another suitable manner. Alternatively, pump 58 may be indirectly connected to the power source ofmachine 10 via a torque converter, a reduction gear box, an electrical circuit, or in any other suitable manner.Pump 58 may produce a stream of pressurized fluid having a pressure level and/or a flow rate determined, at least in part, by demands of the actuators within first andsecond circuits Discharge passage 82 may be connected withinfirst circuit 52 to first andsecond chamber passages swing control valve 56 and first andsecond chamber conduits swing control valve 56 andswing motor 49. -
Tank 60 may constitute a reservoir configured to hold a low-pressure supply of fluid. The fluid may include, for example, a dedicated hydraulic oil, an engine lubrication oil, a transmission lubrication oil, or any other fluid known in the art. One or more hydraulic systems withinmachine 10 may draw fluid from and return fluid totank 60. It is contemplated thathydraulic control system 50 may be connected to multiple separate fluid tanks or to a single tank, as desired.Tank 60 may be fluidly connected to swingcontrol valve 56 via adrain passage 88, and to first andsecond chamber passages swing control valve 56 and first andsecond chamber conduits Tank 60 may also be connected to low-pressure passage 78. Acheck valve 90 may be disposed withindrain passage 88, if desired, to promote a unidirectional flow of fluid intotank 60. -
Swing control valve 56 may have elements that are movable to control the rotation ofswing motor 49 and corresponding swinging motion of implementsystem 14. Specifically,swing control valve 56 may include a firstchamber supply element 92, a firstchamber drain element 94, a secondchamber supply element 96, and a secondchamber drain element 98 all disposed within a common block orhousing 97. The first and secondchamber supply elements discharge passage 82 to regulate filling of their respective chambers with fluid frompump 58, while the first and secondchamber drain elements drain passage 88 to regulate draining of the respective chambers of fluid. Amakeup valve 99, for example a check valve, may be disposed between an outlet of firstchamber drain element 94 andfirst chamber conduit 84 and between an outlet of secondchamber drain element 98 andsecond chamber conduit 86. - To drive
swing motor 49 to rotate in a first direction (shown inFIG. 2 ), firstchamber supply element 92 may be shifted to allow pressurized fluid frompump 58 to enter the first chamber ofswing motor 49 viadischarge passage 82 andfirst chamber conduit 84, while secondchamber drain element 98 may be shifted to allow fluid from the second chamber ofswing motor 49 to drain totank 60 viasecond chamber conduit 86 anddrain passage 88. To driveswing motor 49 to rotate in the opposite direction, secondchamber supply element 96 may be shifted to communicate the second chamber ofswing motor 49 with pressurized fluid frompump 58, while firstchamber drain element 94 may be shifted to allow draining of fluid from the first chamber ofswing motor 49 totank 60. It is contemplated that both the supply and drain functions of swing control valve 56 (i.e., of the four different supply and drain elements) may alternatively be performed by a single valve element associated with the first chamber and a single valve element associated with the second chamber, or by a single valve element associated with both the first and second chambers, if desired. - Supply and drain elements 92-98 of
swing control valve 56 may be solenoid-movable against a spring bias in response to a flow rate and/or position command issued by acontroller 100. In particular,swing motor 49 may rotate at a velocity that corresponds with the flow rate of fluid into and out of the first and second chambers and with a torque that corresponds with a pressure differential acrossimpeller 64. To achieve an operator-desired swing torque, a command based on an assumed or measured pressure drop may be sent to the solenoids (not shown) of supply and drain elements 92-98 that causes them to open an amount corresponding to the necessary fluid flow rates and/or pressure differential atswing motor 49. This command may be in the form of a flow rate command or a valve element position command that is issued bycontroller 100. -
Controller 100 may be in communication with the different components ofhydraulic control system 50 to regulate operations ofmachine 10. For example,controller 100 may be in communication with the elements ofswing control valve 56 infirst circuit 52 and with the elements of control valves (not shown) associated withsecond circuit 54. Based on various operator input and monitored parameters, as will be described in more detail below,controller 100 may be configured to selectively activate the different control valves in a coordinated manner to efficiently carry out operator requested movements of implementsystem 14. -
Controller 100 may include a memory, a secondary storage device, a clock, and one or more processors that cooperate to accomplish a task consistent with the present disclosure. Numerous commercially available microprocessors can be configured to perform the functions ofcontroller 100. It should be appreciated thatcontroller 100 could readily embody a general machine controller capable of controlling numerous other functions ofmachine 10. Various known circuits may be associated withcontroller 100, including signal-conditioning circuitry, communication circuitry, and other appropriate circuitry. It should also be appreciated thatcontroller 100 may include one or more of an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a computer system, and a logic circuit configured to allowcontroller 100 to function in accordance with the present disclosure. - The operational parameters monitored by
controller 100, in one embodiment, may include a pressure of fluid within first and/orsecond circuits more pressure sensors 102 may be strategically located within first chamber and/orsecond chamber conduits controller 100. It is contemplated that any number ofpressure sensors 102 may be placed in any location within first and/orsecond circuits hydraulic control system 50, if desired. -
Hydraulic control system 50 may be fitted with anenergy recovery arrangement 104 that is in communication with at leastfirst circuit 52 and configured to selectively extract and recover energy from waste fluid that is discharged fromswing motor 49. Energy recovery arrangement (ERA) 104 may include, among other things, a recovery valve block (RVB) 106 that is fluidly connectable betweenpump 58 andswing motor 49, afirst accumulator 108 configured to selectively communicate withswing motor 49 viaRVB 106, and asecond accumulator 110 also configured to selectively and directly communicate withswing motor 49. In the disclosed embodiment,RVB 106 may be fixedly and mechanically connectable to one or both ofswing control valve 56 andswing motor 49, for example directly tohousing 62 and/or directly tohousing 97.RVB 106 may include an internalfirst passage 112 fluidly connectable tofirst chamber conduit 84, and an internalsecond passage 114 fluidly connectable tosecond chamber conduit 86.First accumulator 108 may be fluidly connected toRVB 106 via aconduit 116, whilesecond accumulator 110 may be fluidly connectable to low-pressure and drainpassages tank 60, via aconduit 118. -
RVB 106 may house aselector valve 120, acharge valve 122 associated withfirst accumulator 108, and adischarge valve 124 associated withfirst accumulator 108 and disposed in parallel withcharge valve 122.Selector valve 120 may automatically fluidly communicate one of first andsecond passages valves second passages valves controller 100 to fluidly communicatefirst accumulator 108 withselector valve 120 for fluid charging and discharging purposes. -
Selector valve 120 may be a pilot-operated, 2-position, 3-way valve that is automatically movable in response to fluid pressures in first andsecond passages 112, 114 (i.e., in response to a fluid pressures within the first and second chambers of swing motor 49). In particular,selector valve 120 may include avalve element 126 that is movable from a first position (shown inFIG. 2 ) at whichfirst passage 112 is fluidly connected to charge and dischargevalves internal passage 128, toward a second position (not shown) at whichsecond passage 114 is fluidly connected to charge and dischargevalves passage 128. Whenfirst passage 112 is fluidly connected to charge and dischargevalves passage 128, fluid flow throughsecond passage 114 may be inhibited byselector valve 120 and vice versa. First andsecond pilot passages second passages valve element 126 such that a higher-pressure one of first orsecond passages valve element 126 to move and fluidly connect the corresponding passage with charge and dischargevalves passage 128. -
Charge valve 122 may be a solenoid-operated, variable position, 2-way valve that is movable in response to a command fromcontroller 100 to allow fluid frompassage 128 to enterfirst accumulator 108. In particular,charge valve 122 may include avalve element 134 that is movable from a first position (shown inFIG. 2 ) at which fluid flow frompassage 128 intofirst accumulator 108 is inhibited, toward a second position (not shown) at whichpassage 128 is fluidly connected tofirst accumulator 108. Whenvalve element 134 is away from the first position (i.e., in the second position or in an intermediate position between the first and second positions) and a fluid pressure withinpassage 128 exceeds a fluid pressure withinfirst accumulator 108, fluid frompassage 128 may fill (i.e., charge)first accumulator 108.Valve element 134 may be spring-biased toward the first position and movable in response to a command fromcontroller 100 to any position between the first and second positions to thereby vary a flow rate of fluid frompassage 128 intofirst accumulator 108. Acheck valve 136 may be disposed betweencharge valve 122 andfirst accumulator 108 to provide for a unidirectional flow of fluid intoaccumulator 108 viacharge valve 122. -
Discharge valve 124 may be substantially identical to chargevalve 122 in composition, and movable in response to a command fromcontroller 100 to allow fluid fromfirst accumulator 108 to enter passage 128 (i.e., to discharge). In particular,discharge valve 124 may include avalve element 138 that is movable from a first position (not shown) at which fluid flow fromfirst accumulator 108 intopassage 128 is inhibited, toward a second position (shown inFIG. 2 ) at whichfirst accumulator 108 is fluidly connected topassage 128. Whenvalve element 138 is away from the first position (i.e., in the second position or in an intermediate position between the first and second positions) and a fluid pressure withinfirst accumulator 108 exceeds a fluid pressure withinpassage 128, fluid fromfirst accumulator 108 may flow intopassage 128.Valve element 138 may be spring-biased toward the first position and movable in response to a command fromcontroller 100 to any position between the first and second positions to thereby vary a flow rate of fluid fromfirst accumulator 108 intopassage 128. Acheck valve 140 may be disposed betweenfirst accumulator 108 anddischarge valve 124 to provide for a unidirectional flow of fluid fromaccumulator 108 intopassage 128 viadischarge valve 124. - An
additional pressure sensor 102 may be associated withfirst accumulator 108 and configured to generate signals indicative of a pressure of fluid withinfirst accumulator 108, if desired. In the disclosed embodiment, theadditional pressure sensor 102 may be disposed betweenfirst accumulator 108 anddischarge valve 124. It is contemplated, however, that theadditional pressure sensor 102 may alternatively be disposed betweenfirst accumulator 108 andcharge valve 122 or directly connected tofirst accumulator 108, if desired. Signals from thisadditional pressure sensor 102 may be directed tocontroller 100 for use in regulating operation of charge and/or dischargevalves - First and
second accumulators swing motor 49. The compressible gas may include, for example, nitrogen, argon, helium, or another appropriate compressible gas. As fluid in communication with first andsecond accumulators second accumulators accumulators second accumulators conduits second accumulators second accumulators second accumulators - In the disclosed embodiment,
first accumulator 108 may be a larger (i.e., about 5-20 times larger) and higher-pressure (i.e., about 5-60 times higher-pressure) accumulator, as compared tosecond accumulator 110. Specifically,first accumulator 108 may be configured to accumulate up to about 50-100 L of fluid having a pressure in the range of about 260-315 bar, whilesecond accumulator 110 may be configured to accumulate up to about 10 L of fluid having a pressure in the range of about 5-30 bar. In this configuration,first accumulator 108 may be used primarily to assist the motion ofswing motor 49 and to improve machine efficiencies, while second accumulator may be used primarily as a makeup accumulator to help reduce a likelihood of voiding atswing motor 49. It is contemplated, however, that other volumes and pressures may be accommodated by first and/orsecond accumulators -
Controller 100 may be configured to selectively causefirst accumulator 108 to charge and discharge, thereby improving performance ofmachine 10. In particular, a typical swinging motion of implementsystem 14 instituted byswing motor 49 may consist of segments of time during whichswing motor 49 is accelerating a swinging movement of implementsystem 14, and segments of time during whichswing motor 49 is decelerating the swinging movement of implementsystem 14. The acceleration segments may require significant energy fromswing motor 49 that is conventionally realized by way of pressurized fluid supplied to swingmotor 49 bypump 58, while the deceleration segments may produce significant energy in the form of pressurized fluid that is conventionally wasted through discharge totank 60. Both the acceleration and the deceleration segments may requireswing motor 49 to convert significant amounts of hydraulic energy to swing kinetic energy, and vice versa. The fluid passing throughswing motor 49 during deceleration, however, still contains a large amount of energy. The fluid passing throughswing motor 49 may be pressurized during deceleration as a result of restrictions to the flow of the fluid exitingswing motor 49. If the fluid passing throughswing motor 49 is selectively collected withinfirst accumulator 108 during the deceleration segments, this energy can then be returned to (i.e., discharged) and reused byswing motor 49 during the ensuing acceleration segments.Swing motor 49 can be assisted during the acceleration segments by selectively causingfirst accumulator 108 to discharge pressurized fluid into the higher-pressure chamber of swing motor 49 (viadischarge valve 124,passage 128,selector valve 120, and the appropriate one of first andsecond chamber conduits 84, 86), alone or together with high-pressure fluid frompump 58, thereby propellingswing motor 49 at the same or greater rate with less pump power than otherwise possible viapump 58 alone.Swing motor 49 can be assisted during the deceleration segments by selectively causingfirst accumulator 108 to charge with fluid exitingswing motor 49, thereby providing additional resistance to the motion ofswing motor 49 and lowering a restriction and cooling requirement of the fluid exitingswing motor 49. - In an alternative embodiment,
controller 100 may be configured to selectively control charging offirst accumulator 108 withfluid exiting pump 58, as opposed to fluid exitingswing motor 49. That is, during a peak-shaving or economy mode of operation,controller 100 may be configured to causeaccumulator 108 to charge with fluid exiting pump 58 (e.g., viacontrol valve 56, the appropriate one of first andsecond chamber conduits selector valve 120,passage 128, and charge valve 122) whenpump 58 has excess capacity (i.e., a capacity greater than required bycircuits work tool 16 as requested by the operator). Then, during times whenpump 58 has insufficient capacity to adequatelypower swing motor 49, the high-pressure fluid previously collected frompump 58 withinfirst accumulator 108 may be discharged in the manner described above to assistswing motor 49. -
Controller 100 may be configured to regulate the charging and discharging offirst accumulator 108 based on a current or ongoing segment of the excavation, material handling, or other work cycle ofmachine 10. In particular, based on input received from one ormore performance sensors 141,controller 100 may be configured to partition a typical work cycle performed bymachine 10 into a plurality of segments. A typical work cycle may be partitioned, for example, into a dig segment, a swing-to-dump acceleration segment, a swing-to-dump deceleration segment, a dump segment, a swing-to-dig acceleration segment, and a swing-to-dig deceleration segment, as will be described in more detail below. Based on the segment of the excavation work cycle currently being performed,controller 100 may selectively causefirst accumulator 108 to charge or discharge, thereby assistingswing motor 49 during the acceleration and deceleration segments. - One or more maps and/or dynamic elements relating signals from sensor(s) 141 to the different segments of the excavation work cycle may be stored within the memory of
controller 100. Each of these maps may include a collection of data in the form of tables, graphs, and/or equations. The dynamic elements may include integrators, filters, rate limiters, and delay elements. In one example, threshold speeds, cylinder pressures, and/or operator input (i.e., lever position) associated with the start and/or end of one or more of the segments may be stored within the maps. In another example, threshold forces and/or actuator positions associated with the start and/or end of one or more of the segments may be stored within the maps.Controller 100 may be configured to reference the signals from sensor(s) 141 with the maps and filters stored in memory to determine the segment of the excavation work cycle currently being executed, and then regulate the charging and discharging offirst accumulator 108 accordingly.Controller 100 may allow the operator ofmachine 10 to directly modify these maps and/or to select specific maps from available relationship maps stored in the memory ofcontroller 100 to affect segment partitioning and accumulator control, as desired. It is contemplated that the maps may additionally or alternatively be automatically selectable based on modes of machine operation, if desired. - Sensor(s) 141 may be associated with the generally horizontal swinging motion of
work tool 16 imparted by swing motor 49 (i.e., the motion offrame 42 relative to undercarriage member 44). For example,sensor 141 may embody a rotational position or speed sensor associated with the operation ofswing motor 49, an angular position or speed sensor associated with the pivot connection betweenframe 42 andundercarriage member 44, a local or global coordinate position or speed sensor associated with any linkage member connectingwork tool 16 toundercarriage member 44 or withwork tool 16 itself, a displacement sensor associated with movement ofoperator input device 48, or any other type of sensor known in the art that may generate a signal indicative of a swing position, speed, force, or other swing-related parameter ofmachine 10. The signal generated by sensor(s) 141 may be sent to and recorded bycontroller 100 during each excavation work cycle. It is contemplated thatcontroller 100 may derive a swing speed based on a position signal fromsensor 141 and an elapsed period of time, if desired. - Alternatively or additionally, sensor(s) 141 may be associated with the vertical pivoting motion of
work tool 16 imparted by hydraulic cylinders 28 (i.e., associated with the lifting and lowering motions ofboom 24 relative to frame 42). Specifically,sensor 141 may be an angular position or speed sensor associated with a pivot joint betweenboom 24 andframe 42, a displacement sensor associated withhydraulic cylinders 28, a local or global coordinate position or speed sensor associated with any linkage member connectingwork tool 16 to frame 42 or withwork tool 16 itself, a displacement sensor associated with movement ofoperator input device 48, or any other type of sensor known in the art that may generate a signal indicative of a pivoting position or speed ofboom 24. It is contemplated thatcontroller 100 may derive a pivot speed based on a position signal fromsensor 141 and an elapsed period of time, if desired. - In yet an additional embodiment, sensor(s) 141 may be associated with the tilting force of
work tool 16 imparted byhydraulic cylinder 38. Specifically,sensor 141 may be a pressure sensor associated with one or more chambers withinhydraulic cylinder 38 or any other type of sensor known in the art that may generate a signal indicative of a tilting force ofmachine 10 generated during a dig and dump operation ofwork tool 16. - With reference to
FIG. 3 , anexemplary curve 142 may represent a swing speed signal generated by sensor(s) 141 relative to time throughout each segment of an excavation work cycle, for example throughout a work cycle associated with 90° truck loading. During most of the dig segment, the swing speed may typically be about zero (i.e.,machine 10 may generally not swing during a digging operation). At completion of a dig stroke,machine 10 may generally be controlled to swingwork tool 16 toward the waiting haul vehicle 12 (referring toFIG. 1 ). As such, the swing speed ofmachine 10 may begin to increase near the end of the dig segment. As the swing-to-dump segment of the excavation work cycle progresses, the swing speed may accelerate to a maximum whenwork tool 16 is about midway betweendig location 18 and dumplocation 20, and then decelerate toward the end of the swing-to-dump segment. During most of the dump segment, the swing speed may typically be about zero (i.e.,machine 10 may generally not swing during a dumping operation). When dumping is complete,machine 10 may generally be controlled to swingwork tool 16 back toward dig location 18 (referring toFIG. 1 ). As such, the swing speed ofmachine 10 may increase near the end of the dump segment. As the swing-to-dig segment of the excavation cycle progresses, the swing speed may accelerate to a maximum in a direction opposite to the swing direction during the swing-to-dump segment of the excavation cycle. This maximum speed may generally be achieved whenwork tool 16 is about midway betweendump location 20 and diglocation 18. The swing speed ofwork tool 16 may then decelerate toward the end of the swing-to-dig segment, aswork tool 16 nearsdig location 18.Controller 100 may partition a current excavation work cycle into the six segments described above based on signals received from sensor(s) 141 and the maps and filters stored in memory, based on swing speeds, tilt forces, and/or operator input recorded for a previous excavation work cycle, or in any other manner known in the art. -
Controller 100 may selectively causefirst accumulator 108 to charge and to discharge based on the current or ongoing segment of the excavation work cycle. For example, a chart portion 144 (i.e., the lower portion) ofFIG. 3 illustrates 6 different modes of operations during which the excavation cycle can be completed, together with an indication as to whenfirst accumulator 108 is controlled to charge with pressurized fluid (represented by “C”) or to discharge pressurized fluid (represented by “D”) relative to the segments of each excavation work cycle.First accumulator 108 can be controlled to charge with pressurized fluid by movingvalve element 134 ofcharge valve 122 to the second or flow-passing position when the pressure withinpassage 128 is greater than the pressure withinfirst accumulator 108.First accumulator 108 can be controlled to discharge pressurized fluid by movingvalve element 138 ofdischarge valve 124 to the second or flow-passing position when the pressure withinfirst accumulator 108 is greater than the pressure withinpassage 128. - Based on the chart of
FIG. 3 , some general observations may be made. First, it can be seen thatcontroller 100 may inhibitfirst accumulator 108 from receiving or discharging fluid during the dig and dump segments of all of the modes of operation (i.e.,controller 100 may maintainvalve elements Controller 100 may inhibit charging and discharging during the dig and dump segments, as no or little or no swinging motion is required during completion of these portions of the excavation work cycle. Second, the number of segments during whichcontroller 100 causesfirst accumulator 108 to receive fluid may be greater than the number of segments during whichcontroller 100 causesfirst accumulator 108 to discharge fluid for a majority of the modes (e.g., for modes 2-6).Controller 100 may generally causefirst accumulator 108 to charge more often than discharge, because the amount of charge energy available at a sufficiently high pressure (i.e., at a pressure greater than the threshold pressure of first accumulator 108) may be less than an amount of energy required during movement of implementsystem 14. Third, the number of segments during whichcontroller 100 causesfirst accumulator 108 to discharge fluid may never be greater than the number of segments during whichcontroller 100 causesfirst accumulator 108 to receive fluid for all modes. Fourth,controller 100 may causefirst accumulator 108 to discharge fluid during only a swing-to-dig or a swing-to-dump acceleration segment for all modes. Discharge during any other segment of the excavation cycle may only serve to reduce machine efficiency. Fifth,controller 100 may causefirst accumulator 108 to receive fluid during only a swing-to-dig or swing-to-dump deceleration segment for a majority of the modes of operation (e.g., for modes 1-4). -
Mode 1 may correspond with a swing-intensive operation where a significant amount of swing energy is available for storage byfirst accumulator 108. An exemplary swing-intensive operation may include a 150° (or greater) swing operation, such as the truck loading example shown inFIG. 1 , material handling (e.g., using a grapple or magnet), hopper feeding from a nearby pile, or another operation where an operator ofmachine 10 typically requests harsh stop-and-go commands. When operating inmode 1,controller 100 may be configured to causefirst accumulator 108 to discharge fluid to swingmotor 49 during the swing-to-dump acceleration segment, receive fluid fromswing motor 49 during the swing-to-dump deceleration segment, discharge fluid to swingmotor 49 during the swing-to-dig acceleration segment, and receive fluid fromswing motor 49 during the swing-to-dig deceleration segment. -
Controller 100 may be instructed by the operator ofmachine 10 that the first mode of operation is currently in effect (e.g., that truck loading is being performed) or, alternatively,controller 100 may automatically recognize operation in the first mode based on performance ofmachine 10 monitored via sensor(s) 141. For example,controller 100 could monitor swing angle of implementsystem 14 between stopping positions (i.e., between dig and dumplocations 18, 20) and, when the swing angle is repeatedly greater than a threshold angle, for instance greater than about 150°,controller 100 may determine that the first mode of operation is in effect. In another example, manipulation ofinput device 48 could be monitored via sensor(s) 141 to detect “harsh” inputs indicative ofmode 1 operation. In particular, if the input is repeatedly moved from below a low threshold (e.g., about 10% lever command) to above a high threshold level (e.g., about 100% lever command) within a short period of time (e.g., about 0.2 sec or less),input device 48 may be considered to be manipulated in a harsh manner, andcontroller 100 may responsively determine that the first mode of operation is in effect. In a final example,controller 100 may determine that the first mode of operation is in effect based on a cycle and/or value of pressures withinaccumulator 108, for example when a threshold pressure is repetitively reached. In this final example, the threshold pressure may be about 75% of a maximum pressure. - Modes 2-4 may correspond generally with swing operations where only a limited amount of swing energy is available for storage by
first accumulator 108. Exemplary swing operations having a limited amount of energy may include 90° truck loading, 45° trenching, tamping, or slow and smooth craning. During these operations, fluid energy may need to be accumulated from two or more segments of the excavation work cycle before significant discharge of the accumulated energy is possible. It should be noted that, althoughmode 4 is shown as allowing two segments of discharge fromfirst accumulator 108, one segment (e.g., the swing-to-dump segment) may only allow for a partial discharge of accumulated energy. As withmode 1 described above, modes 2-4 may be triggered manually by an operator ofmachine 10 or, alternatively, automatically triggered based on performance ofmachine 10 as monitored via sensor(s) 141. For example, whenmachine 10 is determined to be repeatedly swinging through an angle less than about 100°,controller 100 may determine that one of modes 2-4 is in effect. In another example,controller 100 may determine that modes 2-4 are in effect based on operator requested boom movement less than a threshold amount (e.g., less than about 80% lever command formode 2 or 4), and/or work tool tilting less than a threshold amount (e.g., less than about 80% lever command formode 3 or 4). - During
mode 2,controller 100 may causefirst accumulator 108 to discharge fluid to swingmotor 49 during only the swing-to-dump acceleration segment, receive fluid fromswing motor 49 during the swing-to-dump deceleration segment, and receive fluid fromswing motor 49 during the swing-to-dig deceleration segment. Duringmode 3,controller 100 may causefirst accumulator 108 to receive fluid fromswing motor 49 during the swing-to-dump deceleration segment, discharge fluid to swingmotor 49 during only the swing-to-dig acceleration segment, and receive fluid fromswing motor 49 during the swing-to-dig deceleration segment. Duringmode 4,controller 100 may causefirst accumulator 108 to discharge only a portion of previously-recovered fluid to swingmotor 49 during the swing-to-dump acceleration segment, receive fluid fromswing motor 49 during the swing-to-dump deceleration segment, discharge fluid to swingmotor 49 during the swing-to-dig acceleration segment, and receive fluid fromswing motor 49 during the swing-to-dig deceleration segment. -
Modes swing motor 49 according to operator requests) and stored for use during another segment when less than adequate fluid energy may be available for a desired swinging operation. During these modes of operation,controller 100 may causefirst accumulator 108 to charge with pressurized fluid frompump 58 during a swing acceleration segment, for example during the swing-to-dump or swing-to-dig acceleration segments, when the excess fluid energy is available.Controller 100 may then causefirst accumulator 108 to discharge the accumulated fluid during another acceleration segment when less than adequate energy is available. Specifically, duringmode 5,controller 100 may causefirst accumulator 108 to discharge fluid to swingmotor 49 during only the swing-to-dump acceleration segment, receive fluid fromswing motor 49 during the swing-to-dump deceleration segment, receive fluid frompump 58 during the swing-to-dig acceleration segment, and receive fluid fromswing motor 49 during the swing-to-dig deceleration segment, for a total of three charging segments and one discharging segment. Duringmode 6,controller 100 may causefirst accumulator 108 to receive fluid frompump 58 during the swing-to-dump acceleration segment, receive fluid fromswing motor 49 during the swing-to-dump deceleration segment, discharge fluid to swingmotor 49 during the swing-to-dig acceleration segment, and receive fluid fromswing motor 49 during the swing-to-dig deceleration segment. - It should be noted that
controller 100 may be limited during the charging and discharging offirst accumulator 108 by fluid pressures withinfirst chamber conduit 84,second chamber conduit 86, andfirst accumulator 108. That is, even though a particular segment in the work cycle ofmachine 10 during a particular mode of operation may call for charging or discharging offirst accumulator 108,controller 100 may only be allowed to implement the action when the related pressures have corresponding values. For example, ifsensors 102 indicate that a pressure of fluid withinfirst accumulator 108 is below a pressure of fluid withinfirst chamber conduit 84,controller 100 may not be allowed to initiate discharging offirst accumulator 108 intofirst chamber conduit 84. Similarly, ifsensors 102 indicate that a pressure of fluid withinsecond chamber conduit 86 is less than a pressure of fluid withinfirst accumulator 108,controller 100 may not be allowed to initiate charging offirst accumulator 108 with fluid fromsecond chamber conduit 86. Not only could the exemplary processes be difficult (if not impossible) to implement at particular times when the related pressures are inappropriate, but an attempt to implement the processes could result in undesired machine performance. - During the discharging of pressurized fluid from
first accumulator 108 to swingmotor 49, the fluid exitingswing motor 49 may still have an elevated pressure that, if allowed to drain intotank 60, may be wasted. At this time,second accumulator 110 may be configured to charge with fluid exitingswing motor 49 any time thatfirst accumulator 108 is discharging fluid to swingmotor 49. In addition, during the charging offirst accumulator 108, it may be possible forswing motor 49 to receive too little fluid frompump 58 and, unless otherwise accounted for, the insufficient supply of fluid frompump 58 to swingmotor 49 under these conditions could causeswing motor 49 to cavitate. Accordingly,second accumulator 110 may be configured to discharge to swingmotor 49 any time thatfirst accumulator 108 is charging with fluid fromswing motor 49. - As described above,
second accumulator 110 may discharge fluid any time a pressure within low-pressure passage 78 falls below the pressure of fluid withinsecond accumulator 110. Accordingly, the discharge of fluid fromsecond accumulator 110 intofirst circuit 52 may not be directly regulated viacontroller 100. However, becausesecond accumulator 110 may charge with fluid fromfirst circuit 52 whenever the pressure withindrain passage 88 exceeds the pressure of fluid withinsecond accumulator 110, and becausecontrol valve 56 may affect the pressure withindrain passage 88,controller 100 may have some control over the charging ofsecond accumulator 110 with fluid fromfirst circuit 52 viacontrol valve 56. - In some situations, it may be possible for both first and
second accumulators modes second accumulator 110 to charge with pressurized fluid at the same time that pump 58 is providing pressurized fluid to bothswing motor 49 and to first accumulator 108 (e.g., during the swing-to-dig acceleration segment ofmode 5 and/or during the swing-to-dump acceleration segment of mode 6). At these times, thefluid exiting pump 58 may be directed intofirst accumulator 108, while the fluid exitingswing motor 49 may be directed intosecond accumulator 110. -
Second accumulator 110 may also be charged viasecond circuit 54, if desired. In particular, any time waste fluid from second circuit 54 (i.e., fluid draining fromsecond circuit 54 to tank 60) has a pressure greater than the threshold pressure ofsecond accumulator 110, the waste fluid may be collected withinsecond accumulator 110. In a similar manner, pressurized fluid withinsecond accumulator 110 may be selectively discharged intosecond circuit 54 when the pressure withinsecond circuit 54 falls below the pressure of fluid collected withinsecond accumulator 110. - It may be possible in some situations for
swing motor 49 to stall. In particular, when swingingboom 24, for example betweendig location 18 and dumplocation 20,work tool 16,boom 24,stick 30, and/orframe 42 may engage an immovable object (e.g., a side of a trench, a boulder, another machine, etc.). When this happens, pump 58 may still be pressurizing fluid and directing fluid to a particular chamber ofswing motor 49 according to operator demand (i.e., according to a displacement position of input device 48). While some of this fluid may find leak paths throughswing motor 49, the majority of the fluid will be forced to spill overrelief valves 76 as the pressure offirst circuit 52 rises during the stall. This spillage of high-pressure fluid may be wasteful. Accordingly,controller 100 may be configured to selectively connectRVB 106 withswing motor 49 during a stall event to either charge or dischargefirst accumulator 108 while simultaneously altering operation ofpump 58 to try and recuperate some of the otherwise wasted energy.FIG. 4 illustrates an exemplary method used bycontroller 100 for this purpose.FIG. 4 will be discussed in more detail below to further illustrate the disclosed concepts. - The disclosed hydraulic control system may be applicable to any excavation machine that performs a substantially repetitive work cycle, which involves swinging movements of a work tool. The disclosed hydraulic control system may help to improve machine performance and efficiency by assisting swinging acceleration and deceleration of the work tool with an accumulator during different segments of the work cycle. The unique method used by the disclosed hydraulic control system may help ensure energy recuperation even during a stall event. Operation of the disclosed hydraulic control system will now be described in detail with reference to
FIG. 4 . - As seen in the flowchart of
FIG. 4 ,controller 100 may monitor different operating parameters ofhydraulic control system 50 during operation ofmachine 10. For example,controller 100 may monitor a pressure of fluid atswing motor 49, a lever displacement position ofinput device 48, and a velocity of swing motor 49 (Step 300). Based on this information,controller 100 may determine ifswing motor 49 is experiencing a stall condition (Step 310).Controller 100 may determine thatswing motor 49 is experiencing a stall condition wheninput device 48 is displaced at least a minimum amount indicating an operator's desire forswing motor 49 to rotate, when a significant pressure differential exists across swing motor 49 (i.e., a pressure differential greater than a predetermined amount indicating that significant force is being generated by swing motor 49), and whenswing motor 49 is moving too slow, if at all (i.e., moving at a velocity less than a minimum threshold amount). In one exemplary embodiment, the minimum displacement amount ofinput device 48 may be a displacement of about 10-30% of a maximum displacement; the predetermined pressure differential may be a pressure differential greater than about 200-300 bar; and the minimum threshold velocity may be about 0.1-0.5 rpm. It is contemplated, however, that other ways of determining and/or other values used to determine the stalled condition status ofswing motor 49 may alternatively be utilized, if desired. Whenswing motor 49 is not experiencing the stalled condition, control may return to step 300. - When
swing motor 49 is determined to be stalled (i.e., when the stall conditions described above have been detected),controller 100 may compare a pressure offirst accumulator 108 to one or more threshold pressures (Step 320). In the disclosed exemplary embodiment, two different pressure thresholds may be used, including a first pressure threshold and a second pressure threshold. The first pressure threshold may be about 280 bar and the second pressure threshold may be about 290 bar. - When the pressure of
first accumulator 108 is greater than the second pressure threshold,controller 100 may be configured to close the appropriate first or secondchamber supply valve 92 or 96 (depending on the desired rotational direction of swing motor 49),de-stroke pump 58, and open discharge valve 124 (Step 330). In this situation,first accumulator 108 may have a sufficient store of pressurized fluid and this store may be used as the sole source to driveswing motor 49, thereby saving the otherwise wasted energy that would have been consumed bypump 58. Control may proceed fromstep 330 to step 300. It should be noted that, oncecontroller 100 begins discharge offirst accumulator 108 during a stall event, discharge may continue untilswing motor 49 is no longer stalled or until the pressure offirst accumulator 108 falls below the first pressure threshold. - When the pressure of
first accumulator 108 is below the first pressure threshold (orswing motor 49 first stalls when the pressure offirst accumulator 108 is between the first and second pressure thresholds),controller 100 may be configured to open or maintain open the appropriate first or secondchamber supply valve 92 or 96 (depending on the desired rotational direction of swing motor 49), reduce a displacement ofpump 58, and open charge valve 122 (Step 340). In this situation,first accumulator 108 may have capacity to store additional pressurized fluid, and the reduced output ofpump 58, instead of being wasted could be directed into and stored withinfirst accumulator 108. Control may proceed fromstep 340 to step 300. It should be noted that, oncecontroller 100 begins charging offirst accumulator 108 during a stall event, charging may continue untilswing motor 49 is no longer stalled or until the pressure offirst accumulator 108 rises above the second pressure threshold. - Several benefits may be associated with the disclosed hydraulic control system. First, because
hydraulic control system 50 may utilize a high-pressure accumulator and a low-pressure accumulator (i.e., first andsecond accumulators 108, 110), a large amount of fluid discharged fromswing motor 49 during acceleration segments of the excavation work cycle may be recovered. This double recovery of energy may help to increase the efficiency ofmachine 10. Second, the use ofsecond accumulator 110 may help to reduce the likelihood of voiding atswing motor 49. Third, the ability to adjust accumulator charging and discharging based on a current segment of the excavation work cycle and/or based on a current mode of operation, may allowhydraulic control system 50 to tailor swing performance ofmachine 10 for particular applications, thereby enhancing machine performance and/or further improving machine efficiency. Finally, use of the disclosed method implemented bycontroller 100 during stall events (i.e., during stall of swing motor 49) may further enhance machine efficiency. - It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed hydraulic control system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed hydraulic control system. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
Claims (20)
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US201261695466P | 2012-08-31 | 2012-08-31 | |
US13/718,907 US9328744B2 (en) | 2012-08-31 | 2012-12-18 | Hydraulic control system having swing energy recovery |
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